In general, a bumper beam for a vehicle is configured to be elastically deformed to minimize physical damage to the vehicle upon a low-speed collision thereof. The bumper beam is a buffering means provided at the front and rear of a vehicle so that when a vehicle collides with other vehicles or fixtures, the bumper beam absorbs impact, thereby securing safety of passengers and minimizing deformation of a vehicle body at the same time.
Meanwhile, in order to satisfy pedestrian safety regulations for minimizing injury when a vehicle collides with a pedestrian, a lower stiffener is provided on a lower portion of the bumper beam or a front end module (FEM) carrier.
In the case of the above-mentioned bumper beam and lower stiffener, when strength is increased, weight and costs are rapidly increased, whereas when weight and costs are decreased, strength is decreased and thus a function thereof may be insufficiently performed.
Thus, a fiber-reinforced thermoplastic resin having increased strength while using weight reducing material, such as a glass fiber mat thermoplastic (GMT) material and a continuous fiber reinforced thermoplastic composite tape (CFT) material have been developed.
Herein, the GMT material is a composite material consisting of a polypropylene resin which is a general-purpose resin, and a glass fiber mat reinforcement, and strength of glass fibers itself is reinforced by a mat shape. Further, the CFT material is a composite material consisting of a polypropylene resin which is a general-purpose resin, and continuous fibers, wherein a polymer resin such as PP covers and protects the continuous fibers such that strength of the continuous fibers itself is maintained, whereby the polymer resin is reinforced with the continuous fibers.
The GMT material and the CFT material are novel materials exhibiting superior strength to any existing materials, and have characteristics such as light weight and a degree of freedom in design, which are unique properties of plastic, as well as high productivity, recyclability, and the like, due to the thermoplastic resin.
In recent years, the above-mentioned GMT material and CFT material are being used in various parts of a vehicle because they are lightweight, have excellent collision energy absorption capability, have a high degree of freedom in design, and have excellent assemblability, corrosion resistance, stiffness, stability, sound insulation, vibration damping, elasticity, impact resistance, and the like.
However, since the lower stiffener according to the related art is merely disclosed as a part for satisfying the pedestrian safety regulations rather than an optimal design, it causes weight to be increased when it included in a bumper, and it merely reduces knee bending angle when a vehicle collides with a pedestrian. Accordingly, a structural dynamic approach is not achieved in terms of stiffness and flexibility, leading to an increase in cost and weight.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.